The prior art includes a number of different configurations for single use or one shot thermal switches having fusible pellets that melt at a predetermined temperature, as illustrated by U.S. Pat. Nos. 3,180,958; 3,281,559; 3,519,972; 3,924,218; 4,060,787; 4,068,204; 4,145,654; 4,246,561 and 4,246,564. Several million switches of the type illustrated in FIGS. 1-6 of U.S. Pat. No. 3,519,972 and in U.S. Pat. No. 4,060,787 are utilized each year in small home appliances subject to overheating upon failure, such as coffee makers and hair dryers. These most popular designs, and several of the others, utilize a contact member that is axially slidable within the tubular casing and has a resilient periphery that contacts the inside wall of the casing with a constant radial force. The contact member normally contacts the end of the insulated lead to complete the circuit from the case through the contact element to the lead and upon melting of the fusible pellet the disc is pushed away from the lead to disconnect the circuit. This design has proven highly reliable when the parts are within tolerance and are properly assembled within the switch. However, since the pressure exerted by the periphery of the contact member against the casing is only necessary to reliably complete the electrical connection in the normal state, it would be most desirable if that force would diminish when the temperature was reached at which it was desired to open the circuit so that the contact member could more easily slide in the casing to move away from the electrical lead and disconnect the circuit.